Embodiments of this disclosure generally relate to the field of network communications, and, more particularly, to characteristics of transmitted signals.
Communications technology is evolving to utilize multi-frequency transmissions over a communications medium. For example, in many technologies, such as powerline communications, a transmitting device may send signals via a plurality of frequencies to one or more other devices coupled to the communications medium. Other medium and technologies may also use multi-carrier transmissions in which multiple frequencies are used over a communications channel.
Power spectral density (PSD) refers to power distribution for signals over different frequencies. For example, power may be reduced for a subset of the frequencies used over the communications channel. Reducing power for particular frequencies may also be referred to as “notching” or “filtering.” In some communications medium, certain frequencies are required to be notched (e.g., as a result of regulatory or standardization requirements), and may be referred to as notched, reserved, or rejection bands. PSD constraints (also referred to PSD limit, PSD requirements, or PSD mask) for various frequencies may introduce notches having different notch depths. A notch depth refers to the difference between an un-notched signal power level (for frequencies outside of the notch), and the notched signal power level for frequencies in the notch. In the PSD of a transmitted signal, notch depths may be dependent on PSD requirements, channel quality, or optimization techniques.